Days before a New Jersey drinking-water panel is set to discuss a possible regulation for a contaminant found in Gloucester County water supplies, the plastics company suspected of emitting the chemical placed a full-page newspaper advertisement raising the specter of other potential sources.

A main takeaway of Solvay Specialty Polymer's Thursday ad: A "voluntary and extensive" investigation over the last year shows there are "multiple sources in the region" that might be responsible.

Quickly, in a brief battle of words, the state Department of Environmental Protection countered some of the ad's message, saying that Solvay's work was not over and that it had failed to meet requirements to fully investigate the contamination believed to stem from its West Deptford plant.

"I am extremely disappointed that Solvay Specialty Polymers would suggest that its investigation into perfluorononanoic acid (PFNA) contamination is anywhere near completed," DEP Commissioner Bob Martin said in a statement. "Solvay appears to be trying to absolve itself of any further responsibility when, in fact, we are only in the first phase of investigation."

The company also said research showed the chemical was not found in surface water samples from the Delaware River, though it was found in some sediment samples. The ad further noted that the contaminant was not found in most private drinking-water wells tested.

In a separate news release, Solvay said that it has marked a "milestone" in completing "the elements of the work plan" under the DEP and the federal Environmental Protection Agency. Martin's statement, however, said the company's probe "falls far short of our expectations, neglecting to investigate pathways by which PFNAs have gotten into the area's groundwater," adding that Solvay had not outlined its next steps.

Martin's statement did not address the claim of other possible sources, and a DEP spokesman did not immediately return a request for comment on that aspect Thursday night. Solvay's news release, which followed the advertisement's appearance in the South Jersey Times, said it "anticipates some aspects of the investigation will continue."

The contaminant - a type of perfluorinated chemical (PFC) - has not been the subject of extensive studies, but a scientific panel found a sibling chemical had "probable links" to kidney cancer, thyroid disease, and other illnesses. PFCs have been used to create water- and grease-resistant materials. Solvay said PFNA was used in productions at its West Deptford plant until 2010.

While PFNA is not currently regulated by the state or federal government, the state Drinking Water Quality Institute, an advisory panel to the DEP, is considering proposing a drinking-water standard.

The group's agenda for Wednesday calls for setting a time frame for finalizing a recommended standard, which would require further action by the DEP before implementation.

Since early 2014, five towns - Paulsboro, West Deptford, East Greenwich, Greenwich, and Woodbury - have shut down municipal wells with the chemical because of health concerns.

The DEP installed filters on some private well owners with elevated levels of PFNA. Several residents sued the company. Paulsboro reached a settlement with Solvay under which the company will provide a filtration system for the borough's contaminated well.

Solvay, which has denied responsibility, said in its ad that its actions had been "taken in response to public concerns."

The Delaware Riverkeeper Network, an environmental advocacy group that has pushed for the company to address the contamination, issued a statement Thursday saying that "thousands of people . . . who have had to drink this contaminated water for years without knowing it are not likely to be easily persuaded" by Solvay's advertisement.